|Height||3-1/2 inches||6-1/8 inches|
|Length||5 inches||11-1/2 inches|
|Thickness||0.007 inch||1/4 inch|
Any item smaller than the minimum dimensions is not mailable.
For larger items, see large envelopes or packages.
For envelopes, length is the dimension parallel to the address.
For letter-sized items over 3.5 ounces, large envelope prices will be applied.
Letters that meet one or more of the nonmachinable characteristics below are subject to the nonmachinable surcharge.
The minimum size for a square envelope is 5" x 5".
Square letters are subject to the nonmachinable surcharge.